1. Field of the Invention
The present invention relates to a technique for controlling progress of a video game by displaying a main character and a sub character on an image display screen of an image display apparatus, and by controlling an action of the main character and the sub character displayed on the image display screen in response to operation(s) by a player.
2. Description of the Related Art
Heretofore, various kinds of so-called role playing games (RPG; that is, a game in which a player plays a role of a character in a world of the game, and accomplishes a predetermined object while enjoying a process that the character grows through various experiences) have been provided.
In a video game such as a RPG, generally, the video game proceeds by moving the player character and the like in accordance with operations of a player. Further, in the video game, one friend character or two or more friend characters (hereinafter, referred to as “sub player character” or “sub character”) that acts together with the player character may enter a field.
The sub character is not operated to move directly from the player, but moves to follow a main character (the player character). For this reason, for example, in the case where the main character changes a moving direction when going straight ahead, the sub character also changes a moving direction so as to follow the change of the moving direction. However, in the case where there is an obstacle of the like on a movement route of the sub character, the sub character cannot move due to the obstacle.
Heretofore, there is proposed a video game apparatus that determines whether or not a sub character collides with a sub character using a circumscribed quadrangular shape with respect to an object (for example, see Japanese Patent Application Publication No. 11-175747).
However, the circumscribed quadrangular shape with respect to an object is used in the technique disclosed in the Japanese Patent Application Publication described above. Thus, there was a problem that a processing load for determining whether or not the sub character collides with the obstacle becomes heavy. In the field of technology of processing a video game, there is desire to achieve collision detection or collision determination between an obstacle and a sub character without a heavy processing load.